1. Field of the Invention
The present invention generally relates to data communications and, more particularly, to converting a low voltage AC wiring circuit such as doorbell, or other low voltage control or signaling wiring to a data communications link.
2. Background and Description of the Prior Art
A conventional doorbell system in a residence is very limited in its functionality. If someone in the house wishes to determine the identity of a person at an entrance to a residence, the resident must typically go to the entrance and personally investigate, unless the residence is equipped with an intercom system to enable two-way communication with the person outside the entrance. One problem with the conventional system is that the person inside the house must be present at the door to determine the identity of the visitor. In addition, the conventional system cannot determine the identity of the visitor without disclosing the fact that someone is present inside the house. Further, even with an intercom facility it is not always possible to ascertain with certainty that the person outside the entrance is a person the resident would want to admit inside the house or even to have a conversation with the person.
One prior art solution is to install a closed circuit television system camera at the entrance connected via wiring to a closed circuit TV monitor located within the residence. Such systems tend to be bulky and expensive, and often require technical expertise to install correctly. Another disadvantage of the closed circuit television system is the requirement for additional wiring which may be a substantial expense in many kinds and sizes of residences.
Another prior art solution comprises a unit resembling a desktop telephone having a handset and a display and a second unit resembling a small intercom type unit having a small TV camera, a speaker microphone and a operating control. The camera unit is mounted adjacent the entrance to the residence and the desktop unit is located somewhere within the residence. The two units are connected via dedicated wiring and allows monitoring the entrance and permits two-way communication with the person at the entrance who has rung the doorbell. The call button on the outdoor camera unit may activate an indoor door chime, the camera, and an intercom if it is desired to do so. Even if the visitor does not press the call button but merely knocks on the door, the system has a monitor mode whereby the person inside can activate the camera to provide a visual image of the visitor. This video door phone has the same disadvantage the conventional closed circuit television systems does in that it also requires special wiring and expertise to connect the camera unit to the inside desktop monitoring unit.
Video door chime products similar to those described in the preceding paragraph are also available in versions having a wireless interface between an entry station outside a residence and a receiving station within the residence. While these units provide an alternative to a system that requires the installation of wiring or cabling, such systems tend to be expensive or subject to interference effects with the RF transmission, of the type often encountered with cordless phone products. Such interference can be more troublesome with wireless units because of the greater bandwidth demands placed on a video monitoring system.
What is needed is a system for providing communication between a visitor at an entrance to a residence or business that overcomes the disadvantages noted above and which may be easily installed by a homeowner of average mechanical skills.